Device and process for transferring a material web

ABSTRACT

This invention relates to a device for transferring a material web, particularly a web made of paper, board, tissue, or other pulp. In order to transfer the material web and, preferably, a supporting belt from a first supporting surface to a subsequent supporting surface, a pick-up box with a pick-up zone to lift the material web off the first supporting surface and a stabilizer box with a stabilizing zone to stabilize the material web are arranged before the subsequent supporting surface. Suction can be applied to the pick-up zone and the stabilizing zone by means of a vacuum source. A further zone to separate the vacuum in the pick-up zone from the vacuum in the stabilizing zone is located between the pick-up zone and the stabilizing zone. This invention also relates to a process for transferring a material web performed with the device according to the invention.

BACKGROUND

This invention relates to a device for transferring a material web,particularly a web made of paper, board, tissue, or other pulp. In orderto transfer the material web and, preferably, a supporting belt from afirst supporting surface, for example a drying cylinder, to a subsequentsupporting surface, for example a suction roll, the device has a pick-upbox with a pick-up zone to lift the material web off the firstsupporting surface and a stabilizer box with a stabilizing zone tostabilize the material web before the subsequent supporting surface. Avacuum can be applied to the pick-up zone and stabilizing zone by meansof a vacuum source. This invention also relates to a process fortransferring a material web performed with the device according to theinvention.

Devices of this kind for web transfer are used in the dryer section ofpaper machines, for example. These dryer sections usually consist of anumber of drying cylinders and suction rolls, each of which are arrangedin a row. The web to be dried, supported in a meandering path by anair-permeable supporting belt, runs from a first drying cylinder to asuction roll, round which the web is guided with the aid of vacuum, andon to a further drying cylinder. Here, the web must be transferred inthe areas between the drying cylinders and the suction rolls. Thistransfer takes place using special web transfer devices. Patentapplication EP 1 788 153 A2, for example, describes a web transfer boxwith a pick-up zone and a stabilizing zone. In the pick-up zone, thematerial web and the supporting belt are lifted off the drying cylinderby means of vacuum, and in the stabilizing zone that immediatelyfollows, the material web and supporting belt are stabilized by means ofvacuum. The two vacua in the pick-up zone and the stabilizing zone canbe set and adjusted separately in this process, with the vacuum in thepick-up zone generally being higher than in the stabilizing zone inpractice.

As the stabilizing zone immediately adjoins the pick-up zone and theseal between the zones is often inadequate, the level of vacuum duringoperation in the stabilizing zone is often too high or not at anoptimum. Stronger vacuum in the pick-up zone can create a suction effecton the immediately adjoining stabilizing zone. Too strong a vacuum inthe stabilizing zone, however, causes too much adherence by suction anddeflects the material web and supporting belt. As a result, thesupporting belt is subject to greater wear. It can even rub against theweb transfer box, which can ruin the belt.

The problem could be avoided by reducing the vacuum in the pick-up zoneand thus attuning it to the vacuum in the stabilizing zone, however thiswould not permit efficient operation because different levels of vacuumare required in the individual zones, particularly at high machine andproduction speeds. Due to the ever increasing machine speeds, the webmust be detached even faster from the preceding supporting surface inorder to prevent any negative effect on the web quality.

SUMMARY

The problem thus addressed by the present invention is to create a webtransfer device and transfer process that allows web transfer withoutdeflecting the material web and the supporting web too much in thetransfer area, even at high machine speeds.

This problem is solved by a device in which the pick-up zone of thepick-up box is limited by sealing mechanisms and the stabilizing zone ofthe stabilizing box is limited by a seal and the subsequent supportingsurface, where a further zone to separate the vacuum in the pick-up zonefrom the vacuum in the stabilizing zone is located between the pick-upzone and the stabilizing zone, and is limited by a sealing mechanism inthe pick-up zone and a seal in the stabilizing zone.

This arrangement avoids the vacuum in the pick-up zone having a negativeeffect on the vacuum in the stabilizing zone and the vacuum in thestabilizing zone affecting the vacuum in the pick-up zone.

Thus, the pressures in the pick-up zone and in the stabilizing zone canbe set to the optimum levels so that the web can be lifted off thesupporting surface as close as possible to the tangent point in thepick-up zone and lowest possible wearing forces act on the supportingbelt in the stabilizing zone.

The pick-up box is preferably separated from the stabilizing box. Byseparating the two boxes, it is much easier to install them in the dryersection of a paper machine. It is easier to position these two boxes inrelation to the drying cylinder because each box can be adjustedseparately. In addition, this makes maintenance of the boxes easier, andthere is no need to replace the entire web transfer device in the eventof a fault.

It is advantageous if the take-off box or the stabilizing box has atleast one sealing mechanism that is swivel-mounted. With thisswivel-mounted sealing mechanism it is easy to change a supporting belt.

It makes sense for the pick-up box or the stabilizing box to have atleast one sealing mechanism with several sealing lips, where at leastone space between the sealing lips is connected to a vacuum source. Theseal is crucial in maintaining a certain vacuum level. If strong vacuaare required, a conventional seal is often inadequate. Thus, in order toachieve a suitable result, the air inside the labyrinth chambers orbetween the sealing lips is often extracted by suction. Thus, anadditional vacuum can be maintained and applied in the chambers.

The invention also relates to a corresponding process for transfer of amaterial web, where the material web runs through an additional zonebetween the pick-up zone and the stabilizing zone where the prevailingpressure is higher than the vacuum in the pick-up zone and the vacuum inthe stabilizing zone.

The vacua in the pick-up zone and the stabilizing zone do not affect oneanother here and allow optimum pressure settings for gentle webtransfer, also at high machine speeds.

In a favorable embodiment of the process the vacuum in the pick-up zoneis set at a higher level than the vacuum in the stabilizing zone. Thisensures that the material web can be picked up easily, also at highmachine speeds.

In an advantageous embodiment of the process, suction is applied in atleast one sealing mechanism delimiting the pick-up zone or thestabilizing zone. Since suction is applied to the seal itself, in thespace between the individual sealing lips, an even better sealing effectis achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood and its numerous objectsand advantages will become apparent to those skilled in the art byreference to the accompanying drawings in which:

FIG. 1 is a schematic side view of a web transfer device according tothe invention;

FIG. 2 is an enlarged section of the schematic side view in FIG. 1;

FIG. 3 is a detail of the pick-up box with a swivel-mounted sealingmechanism; and

FIG. 4 is a schematic detail of the pick-up box with a sealing mechanismto which suction is applied.

DETAILED DESCRIPTION

The web transfer device according to the invention is shown in FIG. 1.It comprises a pick-up box 5 and a stabilizing box 7. During operation,the material web 1, coming from the right, is supported on a supportingbelt 2 and guided over a first supporting surface 3, which is a rotatingand heated drying cylinder in the present example. Then the material web1 and the supporting belt 2 are lifted off the first supporting surface3 by the pick-up box 5 in the pick-up zone 6. For this purpose, a vacuumis applied to the pick-up box 5, causing the material web 1 and thesupporting belt 2 to be lifted off the first supporting surface 3 bysuction in the area of the pick-up zone 6. The pick-up zone 6 is sealedoff by means of sealing mechanisms 10 and 10′ that run across themachine running direction. The pick-up zone is adjoined by a furtherzone 9, which is open to the atmosphere in the present example and thushas atmospheric pressure. It is also conceivable that the pressure inthis further zone 9 can be controlled, for example by means of a gatedamper. This further zone 9 is adjoined by the stabilizing zone 8 of thestabilizing box 7. In this stabilizing zone 8, the material web 1 andthe supporting belt 2 are stabilized by means of vacuum. The stabilizingzone 8 is separated from the further zone 9 by a seal 14. Thestabilizing zone 8 is adjoined by the subsequent supporting surface 4,which in the present example is a suction roll. The vacuum applied tothe suction roll ensures that the material web 1 and the supporting belt2 are deflected properly round the suction roll. The suction roll can beconnected directly to the stabilizing box 7, which results in the airfrom the stabilizing box 7 being extracted by means of the suction roll.After the suction roll, the material web 1 and the supporting belt 2 runover a further drying cylinder. The direction of rotation of the twodrying cylinders and of the suction roll is indicated by the arrows.

FIG. 2 shows an enlarged section of the schematic side view of in FIG.1, where the reference numerals used in all figures refer to the sameitems as in FIG. 1. The further zone 9, located between the pick-up zone6 and the stabilizing zone 8, is clearly visible here. The further zone9 is open to the atmosphere in this figure. The pick-up zone 6 is sealedoff at the top and bottom by sealing mechanisms 10 and 10′. The sealingmechanisms 10 and 10′ here consist of individual, blade-like sealinglips 11, which can also form a labyrinth seal. These sealing lips 11 andthe seal 14 can be made of silicone, Teflon, or another syntheticmaterial.

The pick-up box 5 with swivel-mounted sealing mechanisms 10 and 10′ isshown in FIG. 3. The sealing mechanisms 10 and 10′ can be swung out ofthe sealing position by means of an articulated joint 15 and 15′. Thisswing movement can be effected upwards, for example, and/or downwards.The dot-dash lines here show the sealing mechanisms 10 and 10′ swunginto position upwards. By mounting the sealing mechanism 10 suitably atthe pick-up box 5, it is, of course, possible to swing it into positiondownwards (not shown). This swing movement of the sealing mechanism 10,10′ facilitates maintenance work and changing of the supporting belt 2.In addition, the sealing mechanism 10 can yield if the paper wraps rightround the cylinder and thus prevents damage to the sealing lips 11 andthe supporting belt 2. The sealing mechanism 10, 10′ can also bepre-stressed in the sealing position by means of a spring. If thesealing mechanism 10, 10′ moves out of the sealing position, it isreturned to the original sealing position by the pre-stressingmechanism.

FIG. 4 shows a pick-up box 5 with a sealing mechanism 10 to whichsuction is applied. Here, the suction is applied to the space 12 betweenthe sealing lips 11. The air in this space 12 is sucked into the pick-upbox 5 in flow direction 13. During operation, the suction applied to thesealing device 10 provides an improved sealing effect towards theatmosphere and towards the adjoining zone 9, respectively.

The embodiments in the drawings only show one preferred embodiment ofthe invention. The invention also relates to other embodiments in which,for example, the sealing mechanism 10, 10′, which is swivel-mounted orto which suction is applied, is mounted on the stabilizing box 7.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A device for transferring a material web from a first supportingsurface to a subsequent supporting surface, the device comprising: apick-up box having a pick-up zone adapted to lift the material web offthe first supporting surface, the pick-up zone being connected to avacuum source and being limited by first and second sealing mechanisms;a stabilizer box disposed proximate to the subsequent supportingsurface, the stabilizer box having a stabilizing zone connected to avacuum source and being limited by a seal and the subsequent supportingsurface; and a further zone disposed intermediate the pick-up zone andthe stabilizing zone to separate the vacuum in the pick-up zone from thevacuum in the stabilizing zone, the further zone being limited by thesecond sealing mechanism of the pick-up zone and the seal of thestabilizing zone.
 2. The device of claim 1, wherein the pick-up box isdisposed at a distance from the stabilizing box.
 3. The device of claim1, wherein at least one of the sealing mechanisms is swivel-mounted. 4.The device of claim 1, wherein at least one of the sealing mechanismshas a plurality of lips, at least two of the sealing lips defining aspace therebetween, the space being connected to a vacuum source.
 5. Aprocess for transferring a material web from a first supporting surfaceto a subsequent supporting surface, the process comprising: lifting thematerial web off the first supporting surface in a pick-up zone usingvacuum; stabilizing the material web before the subsequent supportingsurface in a stabilizing zone using vacuum; and running the material webthrough an additional zone disposed intermediate the pick-up zone andthe stabilizing zone, the additional zone having a pressure that ishigher than the vacuum in the pick-up zone and the vacuum in thestabilizing zone.
 6. The process of claim 5, wherein the vacuum in thepick-up zone is set at a higher level than the vacuum in the stabilizingzone.
 7. The process of claim 5, further comprising applying a suctionin at least one sealing mechanism delimiting the pick-up zone or thestabilizing zone.